This invention is generally directed to services provided to subscribers in a telecommunication system and is more specifically directed to services provided to a called party subscriber prior to the establishment of communications with the calling party.
Modem telecommunication systems are capable of providing a variety of services for subscribers. Such services can be segregated into services provided prior to call completion and services provided after call completion. Services can be further characterized based upon whether the service is rendered on behalf of the calling or called party. The primary focus of this invention addresses services provided prior to call completion on behalf of the called party.
Depending on the nature of the service to be provided, services can be provided by customer premises equipment such as a telephone instrument, a central office switch, or a computer controlled peripheral device (service node) coupled to the telecommunication network. Subscriber services which are rendered on behalf of the called party prior to the completion of a calling party's call to the called party must be provided by the telecommunication system. Called party features, such as "Selective Call Acceptance", may require the assignment of multiple directory numbers to the called party's line. For the Selective Call Acceptance feature, the central office switch of the called party routes the incoming call request to a service node such as a service circuit node (SCN). The SCN compares the calling party's directory number to a list of directory numbers previously selected by the called party. The call is accepted and routed to the called party only if a match is found. If a match is not found, the calling party is not connected to the called party; the treatment of a nonaccepted call is defined by the telecommunication system, e.g. a prerecorded message could be played to the calling party or the calling party's call could be routed to an answering device. Such preconnection services typically utilize architectures containing a service node for providing such services in cooperation with a central office switch.
In order to provide preconnection services, it may be required to assign the called party two directory numbers. Calls to a published directory number of the subscriber are forwarded to an SCN for possible preconnection call processing; calls to an unpublished directory number known to the SCN are allowed to terminate at the called party's line. For the preconnection services, the central office switch associated with the called party forwards the initial call made to the published directory number to the SCN for processing. The service circuit node, after providing the desired service on behalf of the called party, originates a call to the called party using the unpublished directory number. Upon the called party answering the call placed by the SCN, the service function which may require interaction with the called party is completed while the call request by the original calling party is held in abeyance. Connection of the calling party to the called party may or may not occur depending on the outcome of the service provided and possible interaction between the called party and the SCN. With only a single directory number, all calls made to the subscriber including calls made by the SCN would be forwarded to the SCN. Thus, an undesirable recursive loop between the SCN and the subscriber could occur.
Although the use of multiple directory numbers for a single subscriber permits called party services, assigning multiple directory numbers rapidly depletes the total number of available directory numbers. In locations where a large demand for directory numbers exists, such as in large metropolitan areas, assigning multiple directory numbers depletes a valuable central office switch resource. Thus, there exists a need for techniques that can provide preconnection called party services without requiring the assignment of multiple directory numbers to each subscriber.